Metamitron

Metamitron is an organic compound used as a pesticide.
It has been widely used in the European Union as a selective herbicide in sugar beets for weed suppression since the mid-1970's.
In 2025, the U.S. EPA registered metamitron as a chemical, plant-growth regulator for thinning fruits for use on apple and pear trees.

Chemical Structure and Mode of Action

Metamitron is a triazinone herbicide. It possesses a triazine ring like other organic compounds that use cyanuric chloride as a precursor. It is a modification of the chemical 1,2,4-triazin-5-one, with methyl, amino, and phenyl group substitutions at positions 3, 4, and 6.
Metamitron is in the HRAC Mode of action Group 5. It functions as an inhibitor of PSII by binding to serine 264 on the D1 protein. Resistance to metamitron has been found in Chenopodium album growing as weeds among sugar beet fields in Belgium, caused by a mutation in serine 264.
Metamitron is marketed by ADAMA under the trade name Goltix in Europe, the United Kingdom, New Zealand, and South Africa; and as Brevis™ in the United States.

Health and Environmental Impacts

Metamitron is very toxic to aquatic invertebrates, algae and to higher aquatic plants; and has a low expected acute and long-term toxicity-exposure risk for mammals and herbivorous birds. In humans, metamitron has moderate acute oral and inhalation toxicity and is an endocrine disruptor and may be a thyroid toxicant. The major soil degradation product is desamino-metamitron.